1. Field of the Invention
The present invention relates to an abnormality determination and estimation method for a weld product in a welding process and an abnormality determination and estimation device. For example, an elastic wave generated in a weld product by a welding process is used for determining and estimating an abnormality of the weld product.
2. Description of Related Art
US 2004/0249611 A1 corresponding to JP-A-2004-358487 discloses an abnormality determination and estimation device. The device determines and estimates a presence or absence of an abnormality of a product of a plastic working using an acoustic emission (AE) sensor. The AE sensor can detect an elastic wave generated in a local deformation and destruction.
The AE sensor is provided in a plastic working device, e.g., press die. An elastic wave detected by the AE sensor in each working process is compared with that in non-defective working process. Thus, the device can estimate a determination and discrimination for the abnormalities of the product.
In the device disclosed above, the determination of the abnormality in the product of the plastic working can be easily estimated by providing the AE sensor in the plastic working device, e.g., press die. In contrast, in a welding process, the AE sensor may have to be disposed directly to a weld product, in which metals are welded at a joint portion by heating. This is because the elastic wave is generated when the metals are expanded and contracted by repeating heating and cooling the joint portion. However, if the AE sensor is put on and taken off in each welding process, the process number may be increased such that the productivity may be lowered.
Further, a level of the elastic wave in the welding process may be too small to be detected. Furthermore, in a conventional art, a destruction test may be required for the estimation of the abnormality in the welding process. In the destruction test, generally, the joint portion may have to be destroyed.